A cooler for cooling electric equipment is disclosed in Japanese Patent Application Publication No. 2001-320005 and Japanese Patent Application Publication No. 2002-26215, both of which correspond to U.S. Pat. No. 6,542,365. As shown in FIG. 18, the cooler 9 includes a cooling tube 93. A pair of cooling tubes 93 sandwiches a semiconductor module 92 so that the semiconductor module 92 having a semiconductor chip discharges heat through the cooling tube 93. The semiconductor module 92 and a pair of cooling tubes 93 are fixed with a pair of pinching members 941, 942. Thus, a cooling unit 95 is composed of the semiconductor module 92, a pair of the cooling tube 93, and a pair of pinching members 941, 942. Both sides of the semiconductor module 92 are cooled by a pair of cooling tubes 93.
However, a distance 91 between two neighboring cooling units 95, i.e., the distance 91 between one pair of cooling tubes 93 and another pair of cooling tubes 93 is required to be a predetermined distance, which is equal to or larger than thickness of a pair of pinching members 941, 942. Specifically, the distance 91 is required to be larger than 10 mm. Therefore, dimensions of the cooler 9 become larger. Further, a pair of pinching members 941, 942 is necessitates for every cooling unit 95. Therefore, the number of parts of the cooler 9 becomes larger, and the number of man-hour for assembling the cooler 9 also becomes larger. Thus, a manufacturing cost of the cooler 9 becomes larger.
Further, to minimize the dimensions of the cooler 9, the cooling tube 93 and the semiconductor module 92 are alternately stacked. However, this construction may decrease a cooling performance of the cooler 9. This is because two semiconductor modules 92 are disposed on both sides of the cooling tube 95 so that heat generated in one of the module 92 may transfer to the other module 92 in a case where the heat generated in the one module 92 becomes much larger than that in the other module 92. Further, when the heat generated in each module 92 is different from each other so that thermal expansion of each cooling unit 95 is different. Therefore, load, i.e., stress may be applied partially. Furthermore, when the thickness of each module 92 is different, the variation in a stacking direction may generate the partial stress.
Furthermore, multiple modules 92 are stacked in parallel so that the cooling tubes 95 and the modules 92 are laminated in the stacking direction to form the multi-layered cooler 9. In this case, when the thickness of each module 92 is different from each other, the variation in the stacking direction becomes a problem. Specifically, the total variation of the thickness of cooler 9 becomes larger as the number of the modules 92 becomes larger. Therefore, pinching force of each pair of the pinching members 941, 942 may be different. Thus, heat resistance of contact between the cooling tube 95 and the module 92 becomes larger so that the cooling performance of the cooler 9 is reduced.
Here, the above semiconductor module including power device such as IGBT with a power converter circuit generates large heat. For example, the power converter circuit is suitably used for generating a driving current of an alternating-current motor in an automotive vehicle such as electric driving vehicle and a hybrid vehicle. In this case, the power converter circuit such as DC-DC converter circuit and an inverter circuit energizes the alternating-current motor as a driving power source of the electric vehicle or the hybrid vehicle.
In the cooler disclosed in Japanese Patent Application Publication No. 2002-26215, the semiconductor module is press-contacted to the cooling tube so that a contact area between the cooling tube and the module is increased. However, it is required to add new part for press-contacting the module to the cooling unit. Therefore, the construction of the cooler becomes complicated, and the dimensions of the cooler become larger. Furthermore, the cooler may be deformed in a loading direction so that the dimension accuracy of the cooler is reduced.